Improved method of tempering circular saws



'1. 4UPPmCOTt. A Method of Tempering Circular Saws.

Patented March 5, 1867.

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IMPROVED METHOD 0I' TEMPERING GIRGULAR SAWS.

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TO ALLWHOM -IT MAY GONCERN.:

Be it known that I, JOHN LIPPINCOTLO the city of Pittsburg, in thecounty of Allegheny, and State of Pennsylvania, have invented a new anduseful improvement in Mode of Drawing the' Temperof Saws; and I dolhereby declare thefollowing to be a. full, clear, and exact descriptionthereof, reference being had to the accompanying drawing, forming partof this speciiication, in which- Figure I is a representation of acircular s aw placed upon the carriage used in my mode of drawing thetemper of saws, the saw and carriage being viewed from the under side.

Figure 2 is a vertical section through the centre of the sawandcarriage.

Like letters designate similar parts in both iigures.

It is a matter -of the utmost importance in the manufacture of saws thatall parts of the saw-plate should be of uniform temper; this isespecially the case in large circular saws, which are dillicult andexpensive to malte, because if the saw-plate is of uneven temper, beinghard in some places vand soft Ain others, itis very diiiicult to set theteeth which are too hard, and they frequently break in the operation orcrumble atthe points, while the teeth in the soft portion ofthe platewill not carry an edge or hold the set given to them. This want ofuniformity in the temper of saws is a very common occurrence, andlarises from the practical difficulty of drawing the temper of a steelplate of large diameter by the methods heretofore employed for thatpurpose.

The mode of hardening and tempering saws in general use is to heat themin a furnace and then plunge them in a bath of oil, by which the steelis hardened. -This process has the effect of warping and lrinking thesteel plate to such a degree that its surface becomes very uneven. Thehardened plate is then removed to a furnace .having a level bed, onwhich the saw-plate is laid. It is then exposed to suificien heat todraw the temper down to the proper point.' As it is impossible to havethe furnace'of exactly uniform heat all points, the saw-plate is turnedround and round more or less rapidly by means of long hooked rods,operated by workmen from the open mouth of the furnace, so that noportion of the saw-plate, excepting its centre, continues for anyconsiderable length of" time in the same part of the furnace. This modeof operation would answer the purpose very well if the saw-plate touchedthe bed of the furnace at all points on its surface. This', however, isnot the case, owing to the warped and uneven surface of the saw-plateand as those parte of the plate which are in contact with the bed of thefurnace become more rapidly heated, the temper of those parts is drawndown to the proper point before the other parts of the saw-plate, whichdo not bench the furnace hed, are suiiiciently heated, and thus of'necessity the saw-plate will be harder at seme points than at others.

To remedy this defect is the object of my invention, which consists inelevating the saw-plate above the level of the bed of the furnace insuch a manner that it can be rotated on its axis freely and withoutcoming in contact, at any point at or near its circumference, either'with the furnace or with the device 'used for sup portingfthe saw. l

Another object of my invention is to support the saw-plate intne furnacein such a manner that it can be more easily and rapidly `rotated on itsaxis, and also' be readily inserted into or drawn out of the furnace orbrought to the mouth of. the furnace to enableA the workman to inspectits condition from time to time.

To enable others skilled in the art to use my invention, I will proceedto explainthe manner in which I carry it into practical operation.

In the accompanying drawing, a represents a small carriage, made ofiron, about three inches in height' and about ten or twelve inchessquare, or of such diameter as to Vafford sniiicient support to thesaw-plate without extending too near its periphery. This carriage may befurnished with four wheels, fixed on' axles c, having their bearing inthe sides of the carriage or attached to the under side of the top plateai of the carriage. The top plate d should be a level'snrface. A longrod, e, attached to one end of the carriage, enables it to beconvenientlyoperated in introducing it into the furnace and removing ittherefrom, and. moving yit about fromY place to place within thefurnace. In the centre of the bed-plate is a low vertical spindle,f,which projects upwards from the top' of the carriage and serves as amandrel to receive the saw, the eye of the. saw, which is in the centreof the saw-plate g, receiving the mandrel or spindle f, and the sawplateresting on the top or bed-plate d of the carriage, as shown in fig. 2.The spindle f may be made a separate piece from the carriage andinserted in a suitable hole in the top or bed-plate d.

The mode of operation is es follows: The earriegqfbefore receiving thesaw-pla-te, is placed inside ot' the heated furnace, so as to he asnenrly as possible of the sume temperature as the furnace. It is thendrawn out, and -tlic hardened mwplete is-pla-ced upon it with thcmandrelf inserted through its eye. The carriage is thon wheeled bock into thefurnace, und the workman, oy means-of a hooked rod, turns the scwpluteround end round on its mandi-ei more 'or less rapidly, according to theheat of the furnace. During the process he occasionally 'draws thecarriage to the mouth of the furnace, in order to ascertain hy theappearance ofthe sow when it hee renc-hed the required temper. Circularsaws ore frequently inode six feet in diameter, and by' the old methodof operation it was hard work. for two men to turn the saw on the bed ofthe furnace. By the use of the carriage employed by me for this purpose,owing to the small diameter of the-carriage in comu parison with that ofthe saw, there is but n small port of itssurfnceiin contact with itssupport; one man can manogeit with ease, und the rotation of the saw canbe more constantly maintained, and thereby a much more uniform resultattained. It is` importent to make the surface ofthe carriage on whichthe saw rests as small as is consistent withn suicient support, so cs toleave as large o. portion as possible of the sew-plate towards itscircumference free from contact either with theoarriage or with thebottom of the furnace, because the contact of the Saw-plate with eitherwould tend to withdrew the heut freni that portion of the saw morerapidly, ond thus produce an uneven-'temper'.

I om awarel that steel tools, such as axes, dsc., have been tempered bybeing placed upon. a revolving' metallic wheel, caused to revolve withinu heated furnace, but this would not answer for circular saws, as inthat cese the steel tools ure placed entirely within the circumferenceof the revolving wheel', while my object is t`o place the son as for nspossible outside of the carriage which supports it, and to cause the sewto revolve on and not with its support, so as to obvinte the injuriousefect of contact with another metnllic surface of that portion of thesaw-plate `which necessarily touches the carriage' in which it issupported.

I do not desire to limit myself to the precise vInode of suspending orsupporting the saw within the fur nace hereinbefoie described, os otherdevices might he used; but that which I hnvedeecrihed I have found ontrial to be very successful and convenient, as it not only secures themain object, e uniform temper in the vsaw-plete, but enables the saw tobe more easily handled.

What I claim as my invention, and desire to secure by Letters Potent,is- I 1. A platform for sustaining circular' saws above theloor of thetemperiugd'urnuce, constructed to support by conteo*l the centralportion of the saw only, thus leaving the marginal portion of the sawfree from contact with the platform or with the floor of the furnace,substantially as described.

2. The iron carriage, constructed substantially as herenbeforedescribed, for introducing the saw-plate into the furnace, supportingand adjusting the sume during the process of drawing the temper, und forwithdrawing it from the furnace when the tempering process is completed.

In testimony-whereof, I, the said-JOHN LIP'PlNCOrT, have hereunto set myhand in presence of- JOHN LIPPINOOTT.

Witnesses:

W. D. LEWIS, ALLAN C. Biurnwnnne

